Telecommunication system having means for converting multifrequency

Abstract

A multiplicity of subscriber lines, originating at telephone stations equipped partly with dials and partly with keyboard-controlled multifrequency generators, are connected to pulse-responsive selection equipment by way of switching circuits which are under the control of respective key-signal detectors. Upon the operation of any multifrenquency generator, the latter emits a key signal which actuates the associated detector to switch that line to a conversion network wherein the incoming frequency combinations are translated into binary codes which are stored in a dynamic memory whence they are read out into an available binary/decimal converter. The stored binary codes are accompanied by a line address which enables a coupler to reinsert the selection signals, in the form of digital pulse trains, into the correct line with the aid of an associated interface unit. The selection signals from the subscriber lines and the outputs of the binary/decimal converters are sampled at different rates consistent with the respective numbers of lines and converters. A separate stage in the coupler enables the transmission of data over a line by means of its keyboard upon actuation of an extradigital pushbutton producing a special code.